Howdy folks, been a while eh? I’m back once again with a new power supply review, and hoooo boy have we got a stinker.

I picked this little beauty up at Fry’s for $25, the Zumax X1 ZU-400W power supply.

Right up front we have the bold claim, “DESIGNED BY TOPOWER”. Yeah, right. Topower probably worked as the middleman between the actual manufacturer and Zumax and did the actual importing, but I can tell you for a fact Topower did not design this power supply.

We also have a list of this power supply’s most important features. It has an ATX 20+4 pin cable! Wow, so novel! It also has SATA connectors. Cutting edge! And COLOR BANDS!!!! Yaaaa--wait, what? We’ll get into that in a bit.

First off we know this is an old design, since it has a whopping 30A on the +5V rail, completely excessive for a modern 400W power supply. It claims to have two +12V rails, one 15A and the other 14A. This is a lie, of course.

Seriously, I was so confused when I opened this box. I thought that the “color bands” referred to on the front of the box would be zip ties. Color coded zip ties to help you manage your cables, that’s a nice enough addition, right? But I was wrong! They weren’t zip ties at all!

These are vecro straps in the shape of zip ties and they’re just dreadful. They’re made of the cheapest fabric imaginable and they come all stuck together. The colors are horrible, bright primary colors that I can’t imagine fitting into any conceivable color scheme other than a kindergarten playpen. Just awful. The black ones are the only ones I can see anyone wanting to use. I sure wouldn’t use these for cable management unless my life depended on it. Which would be an interesting situation.

Aside from that, an 18 AWG cable is sufficient for a 400W power supply I suppose, and it does come with two actual zip ties, so that’s something.

The power supply itself has a dull gray case with bright purple stickers. Lovely. It also uses two 80mm fans, which is a fad I thought died out long ago. But no, it looks like 2004 called and they don’t want the ZU-400W back. They say we can have it, no really, please keep it, and have we found the WMDs yet? I told them yes. Am I a bad person?

There’s the usual Cthulu face of cables coming out, but this time it’s much more colorful than I’m used to since none of the cables are sleeved, not even the 20+4 pin. That’s really dreadful. The cables are a mix of 18 and 20 AWG, which is pretty poor, and the 20+4 pin is only about 12 inches long. That’s right, you’ve only got a foot of cable to work with, so forget about cable management and just focus on getting the damn thing to reach your motherboard.

Lovely. You could almost build a Skt 939 system with that, if you were high enough to try.

It also came with several scratches and a smudge of dirt all the way from Guangdong. Exotic.

Without further ado, it’s time to crack this bad boy in half.

Uh, guys? You said this was a Topower PSU, right? Well, it sure doesn’t look like it.

In fact I’m pretty sure that transformer says LP-8867DE. That’s not a Topower part number. That’s a Leadman part number. Yeah. THAT Leadman.

So wow, yeah, looks like we have a real crap in a sack here. Let’s get to work.

The transient filter is pitiful, consisting of only an NTC thermistor for current inrush limitation, one coil, and two Y capacitors. I’ve seen skimpier filters, but not much skimpier. The PCB is marked and drilled for at least one X capacitor, but the part is not present.

The fuse is a little 6.3A, 250V number. Let’s do the math assuming a standard 115V US main. That fuse won’t blow until 725W, well after almost everything else in this power supply is burnt toast. Useless.

The topology is a standard Flyback converter, one of the simplest and, naturally, worst converter types out there. Compared to modern forward and LLC resonant designs, flyback is ridiculously inefficient and noisy (electrically, not acoustically) and is just a poor choice all around. Flyback is acceptable in a $2 cell phone charger. Not in a $25+ PC PSU.

Interestingly, the PCB is marked for four individual diodes for the primary rectification, but the design has been modified to use an all-in-one bridge rectifier part instead. That part is a KBL406G. It is rated for 4A, and is sufficient for the job.

The primary switch is a 2SK3569 N-channel Mosfet, which is rated for 40A pulsed mode at 25C. Yeah, no. Maybe if you were building a 75W notebook adapter. This thing’s no good for a real high power application.

The +5VSB switch is a C5027 rated for 10A pulsed. Adequate.

The primary capacitors are 200V, 470uF electrolytics from Jay’Long, a brand I’m not familiar with

The seconary uses the cheapest design possible for an ATX power supply, grouping the +12V and +5V together on a single coil for regulation, and then using a mosfet to regulate the +3.3V from the +5V. This reduces the number of expensive coils used, so is very popular on bargain bin units. With this design the +12V and +5V usually have atrocious performance, but the +3.3V is usually very clean. This means your RAM stands a chance of surviving when this POS blows up, while your motherboard and CPU, of course, will usually be less lucky.

The +12V is rectified by an MBR20100CT Dual Schottky Rectifier rated for 20A. As we can see, the 29A a user might expect from this unit are a fiction. Also, the design is single rail, so the 15+14 was a lie to begin with. While this part has a maximum value of 20A, I wouldn’t feel comfortable pushing it over 16A long term.

The +5V is regulated by an SBLI6400T Dual Schottky Rectifier. I could not find a datasheet for this component, so the actual rating is unknown, but based on form factor I speculate it is likely a 30A or 40A part. Why didn’t they switch the +12V and +5V regulators so that the rail that actually needs that much power has it? Because they’re cocks.

The +3.3V is mosfet regulated by a 40N03P N-channel Mosfet rated for 40A. Ludicrously over-powered for the +3.3V rail, which would likely not get past 15A load before the +12V rectifier blew up.

Speaking of ludicrously overpowered, how about the +5VSB rail?

That’s the +5VSB rectifier. Now, the +5VSB is a minor rail that powers your system clock and sometimes the USB devices when your computer is in sleep mode. Its typical load is around 0.1 - 2.5A.

This power supply has a 30A SBL3040PT rectifier for it! 30A!!!!!! This part should have been used on the +12V! Instead they used a ludicrously overpowered 30A rectifier for a rail that will never be loaded above 2.5A!!!!! WHY???????

I’ll tell you why. This was originally marked and drilled for a 3A diode, and in earlier versions of this PSU that’s what was used there, and the SBL3040PT was originally used for the +5V rail (see Makalu’s review of the Echostar 680W). However, Topower came along and told Leadman to make some design changes. I doubt any Topower engineer actually had direct input, they probably just told them to use a more powerful part on the +5V rail. So they did. But gosh darnit, what were they going to do with all these extra SBL3040PTs? Well, why not just stick ‘em on the +5VSB rail so they don’t have to order more 3A diodes! Why not? So we find ourselves in the absolutely absurd situation of having a +5VSB rail that can deliver more current than the most important rail in the system, the +12V.

Incredible. Absolutely incredible.

Moving on,

The secondary uses ChengX Low-ESR capacitors for filtration, which are demonstrably among the worst capacitors available in terms of reliability. Great. You know what’s worse? The +12V rail does not have any filter capacitors at all. That’s right. None. Zero. Zip.

There are only six filter capacitors present on the whole power supply, and markings for four more. The +5VSB rail has two caps, the -12V rail has two caps, the +5V rail has one cap, and the +3.3V rail has one cap.

The +12V? Not a single filter capacitor. So all the noise from the primary switch (and keep in mind Flyback topology is notorious for high ripple to begin with), and the noise from the +12V rectifier, all that ripple and noise, is being delivered straight to your components.

I have a feeling if we hooked this thing up to a load tester and oscilloscope, we would see record setting levels of +12V ripple. It might not beat the Linkworld LPSW that JonnyGURU reviewed, but it would probably get close. I’m guessing between 200mV and 600mV at least.

Absolutely terrible.

Solder quality is very bad, very long leads left, and when I removed the PCB a ~1mm ball of solder fell out. I don't know where it came from, but it was loose and if it wedged in the wrong place it could kill the power supply instantly. Absolutely terrible.

And of course the whole thing is regulated by a Texas Instruments LP-7510 PWM controller which supports Over Voltage and Under Voltage protection. This power supply does not have Over Current, Over Power, Over Temperature, or Short Circuit Protection. The fuse might be counted as OPP or SCP, but since it’s rated way too high for the 250W we have here, I’m not counting it.

The two fans are voltage controlled by a two-state switch controlled by a thermistor attached to the secondary heatsink. So it basically has two modes: moderately loud with a high-pitch wine, or full on shrieking banshee.